SAFEGUARDING MECHANICALLY VENTILATED PATIENTS

Backrest elevation just after intubation may help.

Numerous studies have shown that mechanically ventilated patients are at greater risk for aspirating gastric contents, which can lead to the vexing nosocomial infection ventilator-associated pneumonia (VAP). In a recently published study, researchers examined whether an association exists between the height of the head of the patient's bed (backrest elevation) and the development of VAP in that high-risk population.

Sixty-six patients in a respiratory ICU were enrolled in the study, the eligibility criteria being intubation and the implementation of mechanical ventilation within the 24 hours immediately preceding admission, and the absence of both a diagnosis of pneumonia and prior intubation during the current stay in the hospital. Two pressure transducers were attached to the patient's hospital bed to calculate the height of its head in angle degrees, and the researchers analyzed the amount of time that the patient was in a certain position per day, excluding time spent out of the bed (for the purpose of testing, for example).

The presence of VAP was assessed according to a clinical score-derived from data concerning temperature, the white blood cell count, the number of tracheal secretions, oxygenation, the findings of chest radiography, and the results of cultures of tracheal aspirates-that was evaluated at three points: within 24 hours of intubation (at the time of admission into the study), and on the fourth and seventh days of mechanical ventilation. Data on other VAP risk factors, such as the severity of illness (as indicated by the Acute Physiology and Chronic Health Evaluation [APACHE II] score) and oral health status, were also collected for the analysis.

There was a mean duration of 16.2 hours of continuous monitoring on each of the 276 patient days, and the mean backrest elevation was determined to be 21.7[degrees] during the entire study period. Patients were positioned at back-rest elevations of less than 30[degrees] 72% of the time and of less than 10[degrees] 39% of the time. Using a model incorporating the risk factor variables, the backrest elevation, and the patient's APACHE II scores, the researchers concluded that VAP occurred more frequently only in the more severely ill patients positioned at a backrest elevation lower than 30[degrees] during the first 24 hours of intubation.

Although no direct association between the height of the head of the bed alone and the incidence of VAP was found, the researchers suggest that, on the basis of the study findings, that incidence may be diminished by simply maintaining a backrest elevation of at least 30[degrees] during the first 24 hours of mechanical ventilation. They also note that more research is necessary to determine whether the practice might lead to complications such as skin breakdown or the diminished comfort of the patient.

Grap MJ, et al. Am J Crit Care 2005;14(4): 325-32.

ASSESSMENT OF RESPIRATORY RATE IN TRIAGE

Both clinical and electronic measurement can be inaccurate.

Because it serves a fundamental role as an important clinical indicator in an assortment of pulmonary and metabolic conditions, the respiratory rate is considered one of the four vital signs-but it is the only one that still is measured clinically, not electronically, in triage in most EDs in the United States. So, because a patient's respiratory status often guides clinical decisions, researchers in a recently published study sought to determine how accurate the assessments of respiratory rate were during triage in an ED.

The prospective study involved 159 patients, excluding children and the critically ill, who presented consecutively at the ED, during which nurses performed vital sign measurements, including that of the respiratory rate, as part of standard assessment. In the effort to also assess the accuracy of electronic measurement, the research assistants applied leads to the patient's chest to measure the respiratory rate by transthoracic impedance plethysmography. Upon the conclusion of triage, the researchers also performed each of the two "criterion standard" measurements of the respiratory rate recommended by the World Health Organization (WHO)-one minute of auscultation of the chest or one minute's observation.

Complete data on 149 patients, taken from the three sources, were compiled, and variability among them evaluated by a calculation of the standard deviation (SD) in each. The results of the study showed that the variability in the nurses' clinical assessments of respiratory rate was the lowest, at an SD of 3.3, electronic plethymosgraphy yielded an SD of 4.1, and the WHO model yielded an SD of 4.8, indicating that the least deviation was associated with nursing measurement. Both nursing and electronic measurement were found to have a low degree of sensitivity in the detection of abnormal breathing patterns, such as low respiratory rate (fewer than 12 breaths per minute), or a high one (more than 20 breaths per minute). Additionally, both nursing and electronic measurement showed minimal correlation with the WHO model.

Because of the emphasis on the respiratory rate in determining treatment modality, the results of the study are disconcerting. Given the inaccuracy of both the routine clinical measurement of the respiratory rate now used during ED triage and electronic measurement, the researchers recommend that, until the many proposed alternative methods have been investigated and assessed, health care providers in that setting follow the WHO recommendation of a 60-second recording period.

Lovett PB, et al. Ann Emerg Med 2005; 45(1):68-76.

ASTHMA AND INVASIVE PNEUMOCOCCAL DISEASE

Asthma is an independent risk factor.

A person with asthma is at approximately twice the risk for invasive pneumococcal disease (IPD), according to a recently published study.

In the study spanning eight years, data taken from two databases were retrospectively correlated to conduct the analysis, one that captured cases of IPD as part of a surveillance study conducted by the Centers for Disease Control and Prevention, and another that housed data on patients enrolled in Tennessee's state-run managed health care program. The study population consisted of patients (n = 635) between the ages of two and 49 years who had IPD, as identified in the surveillance study, and who had been enrolled for one year prior to diagnosis in the state program. For each patient who met the preceding criteria, 10 age-matched people without IPD were selected at random from the state program to serve as controls.

Researchers analyzed the data for the presence of asthma and other "high-risk" coexisting conditions, as diagnosed in the year preceding the episode of IPD. Further, asthma was classified as either "high risk" or "low risk" according to its severity, as determined by such parameters as the use of [beta] agonists or corticosteroids and the number of hospital admissions and ED visits. In those having high-risk asthma the incidence of IPD was 4.2 episodes per 10,000 patients; in those having low-risk asthma, 2.3 in 10,000; and in those without asthma, 1.2 in 10,000. After adjustment for coexisting conditions and other factors, such as sex and race, the association between asthma and IPD was still significant.

The study results are among the first to highlight a relationship between IPD and asthma, and the authors assert that asthma therefore can be considered an independent risk factor in IPD and that the inclusion of IPD vaccinations in treatment guidelines for asthma may be warranted. They do caution, however, that further research into the subject is necessary, and that a cost-benefit analysis of IPD vaccination should be performed. Further, because the population studied was people of low socioeconomic status, the results may not be applicable to a diverse group of patients.

Talbot TR, et al. N Engl J Med 2005; 352(20):2082-90.